Examination of postoperative peripheral nerve lesions with high-resolution sonography

Peripheral nerve lesions after surgery are common and are related either to direct compromise of the nerve by the surgical procedure (iatrogenic lesions) or to postoperative events such as scar formation. Despite a high sensitivity, electrodiagnosis may not reveal the exact location and cause of a nerve lesion. We hypothesized that high-resolution sonography could be helpful in diagnosing postoperative peripheral nerve lesions by direct visualization of the nerve and surrounding tissues.

Eighteen patients with postoperative peripheral nerve lesions that were confirmed with clinical examination and electrodiagnosis were examined on sonography. Eight patients had lesions caused by direct nerve surgery, and 10 patients had undergone a previous orthopedic operation or open biopsy. Sonographic diagnoses were correlated with neurologic examinations and surgical findings.

Reliable visualization of injured nerves on sonography was feasible in all patients. Axonal swelling of a nerve was diagnosed in three patients, direct compromise of a nerve by surrounding scar tissue or surgical implants was diagnosed in 10 patients, a neuroma was diagnosed in three, and insufficient surgical repair, in two. Sonographic findings were confirmed during surgery in all except one patient.

In contrast to electrophysiologic tests, high-resolution sonography can show the exact location, extent, and type of a postoperative peripheral nerve lesion and the concurrent disease of surrounding tissues. Because the latter can often be the causative agent for the development of a lesion or the lack of improvement with conservative treatment, sonography yields important information that may not be obtained with other diagnostic modalities.